Empirical Model of Radar Scattering in the 3-cm Wavelength Range on the Sea at Wide Incidence Angles

Abstract

We present the results of radar investigation of scattering of electromagnetic radiation in the 3-cm wavelength range by the sea surface in the case of horizontal polarization of the transmitted and received signals and wide incidence angles. Full-scale measurements were performed on the Oceanographic Stationary Platform in the Black Sea in the range of incidence angles from 84.0° to 87.5° at wind velocities from 4 to 19 m/s. Only the conditions of wind waves with no swelling were considered. It is shown that the specific scattering cross section is almost invariant, when the incidence angle varies, but has a strong wind dependence. It can be described by the power function with the exponents 2.8 and 3.8 at the upwind and downwind probing directions, respectively. At weak and moderate winds, the azimuthal dependence of the specific scattering cross section is characterized by the unimodal function with one maximum in the upwind direction and a minimum in the downwind direction. At wind velocities exceeding 10 m/s, the azimuthal dependence of the scattering cross section becomes bimodal and has a minimum at the azimuth being close to the direction perpendicular to the wind (crosswind). The measured values of the specific scattering cross section are approximated by a finite Fourier series with respect to the azimuth, in which the expansion coefficients depend on the wind velocity and inclination angle.